Power management in exercise machine

ABSTRACT

A request is received for a higher torque from a torque controller than is possible from a power supply. The torque controller is coupled to a motor and the power supply, and the motor is coupled to an actuator. The actuator ultimately establishes resistance for a user in an exercise. An energy storage device is discharged to the motor in order to generate the higher torque, wherein the energy storage device is indirectly coupled to the torque controller.

BACKGROUND OF THE INVENTION

Strength training, also referred to as resistance training or weightlifting, is an important part of any exercise routine. It promotes thebuilding of muscle, the burning of fat, and improvement of a number ofmetabolic factors including insulin sensitivity and lipid levels. Manyusers seek a more efficient and safe method of strength training thatallows a large range of weights to lift.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a block diagram illustrating an embodiment of an exercisemachine capable of digital strength training.

FIG. 2A is a block diagram illustrating an embodiment of a system forpower management for an exercise machine.

FIG. 2B is a block diagram illustrating an embodiment of a system forpower management for an exercise machine with more than one motor.

FIG. 2C is a block diagram illustrating an embodiment of a system forpower management for an exercise machine with an alternate energystorage device.

FIG. 3 is a flow chart illustrating an embodiment of a process for powermanagement for an exercise machine.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Using an energy storage device to provide extra power to an exercisemachine is disclosed. The energy storage device is regenerated duringconcentric movements in the exercise machine. The extra power from theenergy storage device may be combined with power from a standardelectrical power supply, enabling the machine to generate higherresistances than would be available by solely relying on the standardelectrical power supply. Alternatively, or in combination, a pulleysystem is used to increase resistance experienced by the user.

The disclosed techniques may be used with any exercise machine, forexample using a digital strength training technique as described in U.S.Provisional Patent Application No. 62/366,573 entitled METHOD ANDAPPARATUS FOR DIGITAL STRENGTH TRAINING filed Jul. 25, 2016 and U.S.patent application Ser. No. 15/655,682 entitled DIGITAL STRENGTHTRAINING filed Jul. 20, 2017, which are incorporated herein by referencefor all purposes. The disclosed techniques may be used withoutlimitation with other exercise machines, and the digital strengthtrainer is given merely as an example embodiment.

An Example Exercise Machine. FIG. 1 is a block diagram illustrating anembodiment of an exercise machine capable of digital strength training.The exercise machine includes the following:

-   -   a controller circuit (104), which may include a processor,        inverter, pulse-width-modulator, and/or a Variable Frequency        Drive (VFD);    -   a motor (106), for example a three-phase brushless DC driven by        the controller circuit;    -   a spool with one or more cables (108) wrapped around the spool        and coupled to the spool. On the other end of the cable an        actuator/handle (110) is coupled in order for a user to grip and        pull on. The spool is coupled to the motor (106) either directly        or via a shaft/belt/chain/gear mechanism. Throughout this        specification, a spool may be also referred to as a “hub”;    -   a filter (102), to digitally control the controller circuit        (104) based on receiving information from the cable (108) and/or        actuator (110);    -   optionally (not shown in FIG. 1) a gearbox between the motor and        spool. Gearboxes multiply torque and/or friction, divide speed,        and/or split power to multiple spools. Without changing the        fundamentals of digital strength training, a number of        combinations of motor and gearbox may be used to achieve the        same end result. A cable-pulley system may be used in place of a        gearbox, and/or a dual motor may be used in place of a gearbox;    -   one or more of the following sensors (not shown in FIG. 1): a        position encoder; a sensor to measure position of the actuator        (110). Examples of position encoders include a hall effect        sensors, magnetic shaft encoders, optical encoders on the        motor/spool/cable (108), an accelerometer in the actuator/handle        (110), optical sensors, position measurement sensors/methods        built directly into the motor (106), and/or optical encoders. In        one embodiment, an optical encoder is used with an encoding        pattern that uses phase to determine direction associated with        the low resolution encoder. Other options that measure back-EMF        (back electromagnetic force) from the motor (106) in order to        calculate position also exist;    -   a motor power sensor; a sensor to measure voltage and/or current        being consumed by the motor (106);    -   a user tension sensor; a torque/tension/strain sensor and/or        gauge to measure how much tension/force is being applied to the        actuator (110) by the user. In one embodiment, a tension sensor        is built into the cable (108). Alternatively, a strain gauge is        built into the motor mount holding the motor (106). As the user        pulls on the actuator (110), this translates into strain on the        motor mount which is measured using a strain gauge in a        Wheatstone bridge configuration. In another embodiment, the        cable (108) is guided through a pulley coupled to a load cell.        In another embodiment, a belt coupling the motor (106) and cable        spool or gearbox (108) is guided through a pulley coupled to a        load cell. In another embodiment, the resistance generated by        the motor (106) is characterized based on the voltage, current,        or frequency input to the motor.

In one embodiment, a three-phase brushless DC (BLDC) motor (106) is usedwith the following:

-   -   a controller circuit (104) combined with filter (102)        comprising:        -   a processor that runs software instructions;        -   three pulse width modulators (PWMs), each with two channels,            or 6 PWMs        -   six transistors in an H-Bridge configuration coupled to the            6 PWM channels;        -   optionally, two or three ADCs (Analog to Digital Converters)            monitoring current on the H-Bridge; and/or        -   optionally, two or three ADCs monitoring back-EMF voltage;    -   a cable (108) wrapped around the body of the motor (106) such        that entire motor (106) rotates, so the body of the motor is        being used as a cable spool in one case. Thus, the motor (106)        is directly coupled to a cable (108) spool. In one embodiment,        the motor (106) is coupled to a cable spool via a shaft,        gearbox, belt, and/or chain, allowing the diameter of the motor        (106) and the diameter of the spool to be independent, as well        as introducing a stage to add a set-up or step-down ratio if        desired. Alternatively, the motor (106) is coupled to two spools        with an apparatus in between to split or share the power between        those two spools. Such an apparatus could include a differential        gearbox, or a pulley configuration; and/or    -   an actuator (110) such as a handle, a bar, a strap, or other        accessory connected directly, indirectly, or via a connector        such as a carabiner to the cable (108).

In one embodiment, the three-phase brushless DC motor (106), may includea synchronous-type and/or asynchronous-type permanent magnet motor, suchthat:

-   -   a. the motor (106) may be in an “out-runner configuration” as        described below;    -   b. the motor (106) may have a maximum torque output of at least        60 Nm and a maximum speed of at least 300 RPMs; and/or    -   c. optionally, with an encoder or other method to measure motor        position.

In some embodiments, the controller circuit (102, 1004) is programmed todrive the motor in a direction such that it draws the cable (108)towards the motor (106). The user pulls on the actuator (110) coupled tocable (108) against the direction of pull of the motor (106).

One purpose of this setup is to provide an experience to a user similarto using a traditional cable-based strength training machine, where thecable is attached to a weight stack being acted on by gravity. Ratherthan the user resisting the pull of gravity, they are instead resistingthe pull of the motor (106).

Note that with a traditional cable-based strength training machine, aweight stack may be moving in two directions: away from the ground ortowards the ground. When a user pulls with sufficient tension, theweight stack rises, and as that user reduces tension, gravity overpowersthe user and the weight stack returns to the ground.

By contrast in a digital strength trainer, there is no actual weightstack. The notion of the weight stack is one modeled by the system. Thephysical embodiment is an actuator (110) coupled to a cable (108)coupled to a motor (106). A “weight moving” is instead translated into amotor rotating. As the circumference of the spool is known and how fastit is rotating is known, the linear motion of the cable may becalculated to provide an equivalency to the linear motion of a weightstack. Each rotation of the spool equals a linear motion of onecircumference or 2πr for radius r. Likewise, torque of the motor (106)may be converted into linear force by multiplying it by radius r.

If the virtual/perceived “weight stack” is moving away from the ground,motor (106) rotates in one direction. If the “weight stack” is movingtowards the ground, motor (106) rotates in the opposite direction. Notethat the motor (106) is pulling towards the cable (108) onto the spool.If the cable (108) is unspooling, it is because a user has overpoweredthe motor (106). Thus, note a distinction between the direction themotor (106) is pulling, and the direction the motor (106) is actuallyturning.

If the controller circuit (102, 1004) is set to drive the motor (106)with, for example, a constant torque in the direction that spools thecable, corresponding to the same direction as a weight stack beingpulled towards the ground, then this translates to a specificforce/tension on the cable (108) and actuator (110). Calling this force“Target Tension”, this force may be calculated as a function of torquemultiplied by the radius of the spool that the cable (108) is wrappedaround, accounting for any additional stages such as gear boxes or beltsthat may affect the relationship between cable tension and torque. If auser pulls on the actuator (110) with more force than the TargetTension, then that user overcomes the motor (106) and the cable (108)unspools moving towards that user, being the virtual equivalent of theweight stack rising. However, if that user applies less tension than theTarget Tension, then the motor (106) overcomes the user and the cable(108) spools onto and moves towards the motor (106), being the virtualequivalent of the weight stack returning.

While many motors exist that run in thousands of revolutions per second,an application such as fitness equipment designed for strength traininghas different requirements and is by comparison a low speed, high torquetype application suitable for a BLDC motor.

In one embodiment, a requirement of such a motor (106) is that a cable(108) wrapped around a spool of a given diameter, directly coupled to amotor (106), behaves like a 200 lbs weight stack, with the user pullingthe cable at a maximum linear speed of 62 inches per second. A number ofmotor parameters may be calculated based on the diameter of the spool.

User Requirements Target Weight 200 lbs Target Speed  62 inches/sec =1.5748 meters/sec Requirements by Spool Size Diameter (inches) 3 5 6 7 89 RPM 394.7159 236.82954 197.35795 169.1639572 148.0184625 131.5719667Torque (Nm) 67.79 112.9833333 135.58 158.1766667 180.7733333 203.37Circumference 9.4245 15.7075 18.849 21.9905 25.132 28.2735 (inches)

Thus, a motor with 67.79 Nm of force and a top speed of 395 RPM, coupledto a spool with a 3 inch diameter meets these requirements. 395 RPM isslower than most motors available, and 68 Nm is more torque than mostmotors on the market as well. E-bike motors may be in the 350 to 450 RPMrange, but many top out around 50-60 Nm if they are wound for that speedrange. The internal motor windings may be used to trade off motor speedvs torque as well as external mechanical advantage.

Hub motors are three-phase permanent magnet BLDC direct drive motors inan “out-runner” configuration: throughout this specification out-runnermeans that the permanent magnets are placed outside the stator ratherthan inside, as opposed to many motors which have a permanent magnetrotor placed on the inside of the stator as they are designed more forspeed than for torque. Out-runners have the magnets on the outside,allowing for a larger magnet and pole count and are designed for torqueover speed. Another way to describe an out-runner configuration is whenthe shaft is fixed and the body of the motor rotates.

Hub motors also tend to be “pancake style”. As described herein, pancakemotors are higher in diameter and lower in depth than most motors.Pancake style motors are advantageous for a wall mount, subfloor mount,and/or floor mount application where maintaining a low depth isdesirable, such as a piece of fitness equipment to be mounted in aconsumer's home or in an exercise facility/area. As described herein, apancake motor is a motor that has a diameter higher than twice itsdepth. As described herein, a pancake motor is between 15 and 60centimeters in diameter, for example 25 centimeters in diameter, with adepth between 6 and 50 centimeters, for example a depth of 6.7centimeters.

Motors may also be “direct drive”, meaning that the motor does notincorporate or require a gear box stage. Depending on the internalnumber turns and number of windings it is possible to tradeoff torqueand speed. Many motors are inherently high speed low torque butincorporate an internal gearbox to gear down the motor to a lower speedwith higher torque and may be called gear motors. Direct drive motorsmay be explicitly called as such to indicate that they are not gearmotors.

If a motor does not exactly meet the requirements illustrated in thetable above, the ratio between speed and torque may be adjusted by usinggears or belts to adjust. A motor coupled to a 9″ sprocket, coupled viaa belt to a spool coupled to a 4.5″ sprocket doubles the speed andhalves the torque of the motor. Alternately, a 2:1 gear ratio may beused to accomplish the same thing. Likewise, the diameter of the spoolmay be adjusted to accomplish the same.

Alternately, a motor with 100× the speed and 100th the torque may alsobe used with a 100:1 gearbox. As such a gearbox also multiplies thefriction and/or motor inertia by 100×, torque control schemes becomechallenging to design for fitness equipment/strength trainingapplications. Friction may then dominate what a user experiences. Inother applications friction may be present, but is low enough that it iscompensated for, but when it becomes dominant, it is difficult tocontrol for. For these reasons, direct control of motor speed and/ormotor position as with BLDC motors is more appropriate for fitnessequipment/strength training systems.

Power Management in an Exercise Machine.

In one embodiment, the exercise machine depicted in FIG. 1 is limited to200 lb on the cable (108). Athletes may be able to exert 200 lb ofresistance force on an actuator at a maximum speed of 90 inches persecond. One goal is to be able to double this capacity temporarily andsupport professional athletes who may be able to exert 400 lb ofresistance force on the actuator at a maximum speed of 180 inches persecond. In one embodiment, there are two cables (108) in the exercisemachine, one per arm, with 1001 b resistance on each cable (108), and2001 b total.

A first reason for this limit may concern physical risks, for examplethe cable (108) being pulled against an extended arm, causing hightorque against the physical connection between the exercise machine andthe wall.

A second reason concerns the limits of standard electrical supply. Asreferred to herein without limitation, a “standard” electrical supply isany electrical supply at a predetermined capacity, for example that of ageneral-purpose circuit size for a US residence of 110V-125V at 15A, ora European or Chinese residence of 220V-250V at 10A. Even if physicalrisks in the first reason are reduced, electrical limits still exist forexercise machines to be compatible with a larger percentage ofresidences.

A typical standard circuit in the USA rated for 120V and 15A may provide1800 W of input AC power, and after conversion and losses there isapproximately 1500 W of power available for driving a motor basedexercise system. In other countries the power from a standardresidential circuit also has similar limits.

Higher power circuits may be available in any home but are only in a fewrooms like laundry rooms, kitchens, garages, or closets. Relying on ahigher power circuit would prohibit installation in most rooms orinvolve costly renovations that would significantly reduce the marketfor an exercise machine as in FIG. 1. Even with a costly renovation, alarger power supply for the exercise machine to handle higher powercircuits are less common and present a greater expense to manufacturingexercise machines.

Thus, a standard circuit provides about 1500 W of power to drive a motorbased exercise system which is around 200 lb of total resistance. Thismay not be enough for many athletes, for example professional athletesmay be able to deadlift 400 lb. That is, the average power outputcapability of professional athletes may be approximately 400 Wcontinuous for lhr, however their instantaneous power may be 10 timesthat amount in the case of weight lifting. It is this instantaneous orinrush power requirement where the need for a power boost comes in.

In the case of digital strength training, beyond resistance there isalso a speed of movement component to make the exercise feel natural andeffective. In general, mechanical advantage systems like a gearingsystem or motor design may be used to increase resistance at the expenseof speed, but the fact remains that some movements are both heavy andfast.

Increasing both the maximum resistance and speed of the exercise machinewithout requiring a change in the electrical connection for the machineis disclosed. Instead of using an energy storage device solely forbackup purposes or to drive auxiliary devices, for example during apower outage, the energy storage device may be used also for boostingthe power of the exercise machine beyond that available from theelectrical connection. The energy storage device may be charged throughuse of the exercise machine.

FIG. 2A is a block diagram illustrating an embodiment of a system forpower management for an exercise machine. A motor (106) system is shownin FIG. 2 with associated actuator (110) and motor controller (104).

Motors (106) are limited by the torque and speed that they can generatefor a given power input. The tradeoff means that as torque is increasedthen speed is reduced. To meet the force and speed requirements forexercise equipment where both fast and slow movements and heavy andlight forces are needed a motor may be designed appropriately. Typicallymotors that may meet both these requirements use between 1000-1500 W ofpower.

When using multiple motors simultaneously it may no longer be possibleto simply draw this much power from a standard household AC (alternatingcurrent) circuit. Storing energy in an appropriately sized energystorage device (204) to boost the available power to be able to drivemultiple high power motors (106) to their full peak force is disclosed.As referred to herein, an “energy storage device” includes any devicecapable of energy storage including without limitation a sealedlead-acid battery, absorbent glass mat (AGM) battery, gel battery, adeep cycle battery, a marine battery, a lithium-ion battery, a lithiumiron phosphate battery, a capacitor, and a supercapacitor. In FIG. 2A,the example of a lithium-ion battery is given.

Motor controllers (104) take power first from the power supply unit(242) which is coupled through a blocking diode (244) to the main powerrail (246). The PSU (242) is coupled directly to a standard AC input(243), for example a 120V 15A household circuit. In the event it isdetected via voltage sense (201) that the main power rail (246) droopsin voltage because the PSU (242) cannot supply sufficient energy/currentthen the power management module (202) steps in.

For the purposes of illustration, a main power rail (246) of 48V is usedwithout limitation. For example, a PSU (242) may be a 48V, 32A constantcurrent PSU. A corresponding Li-Ion battery (204) may be a 48.1V 13S4P18650 35A battery with at least 10 Ah. In one embodiment, LiFePO4 andLiFeMnPO4 batteries are used for the lithium chemistry. Otherchemistries may not be as stable for high charge/discharge currents, butthese other chemistries have higher volume to charge ratios.

Under voltage switch (206), its associated diode (208) enables energy toflow from the energy storage device (204) to boost motors to be driventowards the desired force. For example, a 47.5 Volt under voltage switch(206) may be used for a main power rail (246) of 48V. If the energystorage device (204) is fully charged then the energy storage device(204) is used first to bring the device (204) to a nominal charge levelinstead of drawing initially from the PSU (242) for appropriatemaintenance of the storage technology of energy storage device (204). Atrickle charger (222) and associated diode (224) is used to charge theenergy storage device (204) in order to conduct appropriate charging anddischarging care and maintenance of the Li-Ion battery (204). A one tofive Ampere trickle charger (222) may be used when the energy storagedevice (204) goes below 30% total charge until it reaches 50% totalcharge. In one embodiment, trickle charging is not from a separatesupply but sourced from the main 48V supply, for example the 48V isboosted by the trickle charger to match the required charge voltage.

In the event the user is pulling against the direction of resistance bya motor (106), that is, in the concentric direction, then the motor(106) acts as a generator to recharge the energy storage device (204).The faster/harder the motor (106) is turned by the user via the actuator(110), the more power generated. As the motor (106) generates power themotor controller (104) feeds it back into the main rail (246) causingthe voltage to rise.

As the voltage increase in the main rail (246) is detected by voltagesense (201), an over voltage switch (210) and associated diode (212)enables energy/current to flow into the charging path of the energystorage device (204) optionally through a Coulomb counter (214). Forexample, a 48.5 Volt over voltage switch (210) may be used for a mainpower rail (246) of 48V. If the current exceeds the charging capabilityof the energy storage device (204), for example as detected by anoptional current limiter (220), or if the energy storage device (204)has reached capacity as detected by the Coulomb counter (214) or othermeans, then excess energy/current is dumped via optional charge dump(216) into shunt resistor (218). For example, a current limiter may havea voltage rating of 100V.

The shunt resistor (218) may be used to maintain the Li-Ion battery(204) within given charging and discharging characteristics. Forexample, if the battery (204) goes above 80% total charge, the shuntresistor (218) may be used to discharge the battery (204) to 50% totalcharge. In one embodiment (not shown), instead or in conjunction withthe shunt resistor (218), excess energy is fed back to an AC householdsystem with an AC inverter, or used as a charging outlet for a user toplug in their own devices.

Sizing of the energy storage device (204) may be specific to the usecase of an exercise machine. In one embodiment, for a cable basedexercise machine it is assumed a duty cycle of approximately 50% rest,20% concentric, 30% eccentric or holding. For a 1500 W PSU, about themaximum that a standard circuit can supply, an exercise machine powermanagement module (202) is designed to supply 3000 W at peak loads.

During a 400 lb concentric pull, each motor of two motors (106 a, 106 b)may generate up to 60 Amperes. The energy storage device (204) maysupport an overall peak drain of 3000 W so that the excess 1500 Wsupplied by the energy storage device (204) corresponds to 1500 W/48V=32A discharge current, with as high a peak charge rate for shortdurations as possible to capture as much of the user generated powerquickly. In one embodiment, the energy storage device (204) has acapacity sufficient to boost power for the maximum expected duration andduty cycle of the high power demand, for example a capacity in the rangeof 100 Wh to 250 Wh.

In one embodiment, pulleys are used to multiply or divide resistanceexperienced by the user at the cost of the speed of the motor. Insteadof attaching the end of the rope directly to a handle, bar, or anotherattachment, the end of the rope may be fixed to the ground, a platform,the machine itself, or another fixed or moving object. The rope may thenflow through one or more pulleys to multiply or divide the forceexperienced by the user relative to the force being created by thetorque of the motor. The pulleys may be attached to the handle, bar, orother attachment and to other fixed or moving parts of the system tocreate the desired force multiple.

FIG. 2B is a block diagram illustrating an embodiment of a system forpower management for an exercise machine with more than one motor. Forexample, a motor (106 a, 106 b) system is shown in FIG. 2B withassociated actuator (110 a, 110 b) and motor controller (104 a, 104 b),one motor system per arm of the user. The same principles describedabove and/or depicted in FIG. 2A may be adapted to the system in FIG.2B.

FIG. 2C is a block diagram illustrating an embodiment of a system forpower management for an exercise machine with an alternate energystorage device. For example, a sealed lead acid battery (204) is used,such as a 48V AGM battery. The same principles described above and/ordepicted in FIG. 2A may be adapted to the system in FIG. 2C, wherein thetrickle charger (222) and shunt resistor (218) may be altered to adaptto the sealed lead acid battery technology and best practices forcharging and discharging characteristics.

FIG. 3 is a flow chart illustrating an embodiment of a process for powermanagement for an exercise machine. In one embodiment, the process ofFIG. 3 is carried out by the power management module (202) of FIG. 2.

In step 302, a request is received for a higher torque from a torquecontroller (104) than is possible from a power supply (242), wherein thetorque controller (104) is coupled to a motor (106) and the power supply(242), and the motor (106) is coupled to an actuator (110), and theactuator (110) ultimately establishes resistance for a user in anexercise. In one embodiment, the “request” is received by sensing adrooping voltage along a main power rail (246).

In step 304, an energy storage device (204) is discharged to the motor(106) in order to generate the higher torque, wherein the energy storagedevice (204) is indirectly coupled to the torque controller (104).

The actuator (110) is coupled via a cable to the motor (106). The powersupply (242) is coupled to a standard household AC power circuit (243).The standard household AC power circuit (243) comprises any circuit withpower less than 2000 Watts.

The energy storage device (204) comprises at least one of the following:a sealed lead-acid battery, a deep cycle battery, a marine battery, alithium-ion battery, a lithium iron phosphate battery, a capacitor, anda supercapacitor. A trickle charger (222) coupled to the power supply(242) and to the energy storage device (204), is configured to safelycharge the energy storage device (204) in an event the energy storagedevice (204) has less than a predefined charge.

An over voltage switch (210) coupled to the power supply (242) and theenergy storage device (204), is configured to safely charge the energystorage device (204) in an event a user increases a main power railvoltage (246) by exercising the actuator (110). The motor (106) may beused instead of a shunt (218) to discharge the energy storage devicewhen the motor is not in use. The motor may burn off excess energy bypassing DC or the equivalent of DC through PWM control. Passing DCthrough the motor may not allow the motor to move. This may allow foreither a smaller wattage shunt or complete remove with the propermanagement of the exercise, that is requiring a rest period afterexcessive energy generation. In one embodiment, a charge dump includesan AC inverter, shunt, DC passing through motor, and 12V/USB charger.

A charge dump (216) coupled to the over voltage switch (210) isconfigured to safely dump charge in an event a charge is too much forthe energy storage device (204). In one embodiment, the charge dump(216) includes a consumer charging station for charging consumerdevices. In one embodiment, the charge dump (216) includes an ACinverter for feedback into an AC household system. For example, it maypower household devices once the house electrical system is isolatedfrom utility power from the exercise machine, provided the system has anDC to AC inverter. The exercise machine may also operate at reduced loadsuch as 501 bs per arm in this mode.

An under voltage switch (206) coupled to the power supply and the energystorage device, is configured to safely discharge the energy storagedevice (204) in an event a user decreases a main power rail voltage(246) by exercising the actuator (110). The main power rail (246)associated with the power supply (242) is set between 47.5 Volts and48.5 Volts. In one embodiment, the power supply (242) can provide up to200 lb of resistance force for the actuator (110).

The electrical storage device (204) has sufficient capacity anddischarge current such that the electrical storage device (204) andpower supply (242) together can provide up to 400 lb of resistance forcefor the actuator (110). In one embodiment, the electrical storage device(204) is rated for more than 32 Amperes of peak discharge current. Inone embodiment, the electrical storage device (204) is rated for morethan 6 Amperes of peak discharge current.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. An exercise machine comprising: a motor; anactuator coupled to the motor, wherein the actuator ultimatelyestablishes resistance for a user in an exercise; a torque controllercoupled to a power supply and to the motor; and an energy storage deviceindirectly coupled to the torque controller, wherein if a higher torqueis requested by the torque controller than is possible from the powersupply, the energy storage device is discharged to the motor in order togenerate higher torque.
 2. The exercise machine of claim 1, wherein theactuator is coupled via a cable to the motor.
 3. The exercise machine ofclaim 1, wherein the power supply is coupled to a standard household ACpower circuit.
 4. The exercise machine of claim 3, wherein the standardhousehold AC power circuit comprises any circuit with power less than2000 Watts.
 5. The exercise machine of claim 3, wherein the standardhousehold AC power circuit comprises any US circuit with amperagebetween 12 Amperes and 16 Amperes.
 6. The exercise machine of claim 3,wherein the standard household AC power circuit comprises anyEuropean/Chinese circuit with amperage between 8 Amperes and 12 Amperes.7. The exercise machine of claim 1, wherein the energy storage devicecomprises at least one of the following: a sealed lead-acid battery, adeep cycle battery, a marine battery, a lithium-ion battery, a lithiumiron phosphate battery, a capacitor, and a supercapacitor.
 8. Theexercise machine of claim 1, further comprising a trickle chargercoupled to the power supply and to the energy storage device, configuredto safely charge the energy storage device in an event the energystorage device has less than a predefined charge.
 9. The exercisemachine of claim 1, further comprising an over voltage switch coupled tothe power supply and the energy storage device, configured to safelycharge the energy storage device in an event a user increases a mainpower rail voltage by exercising the actuator.
 10. The exercise machineof claim 9, further comprising a charge dump coupled to the over voltageswitch configured to safely dump charge in an event a charge is too muchfor the energy storage device.
 11. The exercise machine of claim 10,wherein the charge dump includes a consumer charging station forcharging consumer devices.
 12. The exercise machine of claim 10, wherein the charge dump includes using the motor in DC mode to discharge theenergy storage device.
 13. The exercise machine of claim 10, wherein thecharge dump includes an AC inverter for feedback into an AC householdsystem.
 14. The exercise machine of claim 1, further comprising an undervoltage switch coupled to the power supply and the energy storagedevice, configured to safely discharge the energy storage device in anevent a user decreases a main power rail voltage by exercising theactuator.
 15. The exercise machine of claim 1, wherein a main power railassociated with the power supply is set between 23.5 Volts and 120.5Volts.
 16. The exercise machine of claim 1, wherein the power supply israted below 1800 watts.
 17. The exercise machine of claim 1, furthercomprising a second actuator, a second motor, and second torquecontroller, wherein the second motor is coupled to the second actuatorand the second torque controller, and the second torque controller iscoupled to the power supply.
 18. The exercise machine of claim 1,wherein the power supply can provide up to 200 lb of resistance forcefor the actuator at a maximum speed of 90 inches per second.
 19. Theexercise machine of claim 1, wherein the electrical storage device hassufficient capacity and discharge current such that the electricalstorage device and power supply together can provide up to 400 lb ofresistance force for the actuator at a maximum speed of 180 inches persecond.
 20. The exercise machine of claim 19, wherein the electricalstorage device is rated for between 6 Amperes and 60 Amperes of peakdischarge current.
 21. The exercise machine of claim 19, wherein theelectrical storage device is rated to boost torque by more than 20%. 22.A method, comprising: receiving a request for a higher torque from atorque controller than is possible from a power supply, wherein: thetorque controller is coupled to a motor and the power supply, and themotor is coupled to an actuator; and the actuator ultimately establishesresistance for a user in an exercise; and discharging an energy storagedevice to the motor in order to generate the higher torque, wherein theenergy storage device is indirectly coupled to the torque controller.